Good manufacturing practices (GMP) and governmental regulations are key to any pharmaceutical or biotechnological development or manufacturing process or procedure today. Such processes and procedures, together with the associated equipment, must undergo mandatory validation and qualification procedures to satisfy the regulatory authorities. Thus, for example, the equipment used for the separation and purification of biomedical products, such as preparative chromatography or tangential flow filtration systems, must meet stringent cleanliness requirements involving multiple tests for microbiological contamination. Additional safeguards must also be implemented to avoid chemical cross-contamination between product runs using the same equipment. These procedures are both costly and time consuming.
In order to reduce such cleaning and validation costs and expenses, the pharmaceutical and biotechnology industries are increasingly using pre-sterilised, single-use or disposable equipment in their separation and purification processes. There is therefore a need for inexpensive, disposable sensors which can be pre-sterilised and used in such processes.
Disposable pressure transducers are commonly used in medical environments for measuring body fluid pressures, particularly blood pressures, outside the patient's body. These transducers typically consist of a disposable part, which is inexpensive to manufacture, and a reusable part which comprises the expensive, electronic sensor. The disposable part generally consists of a flexible membrane or diaphragm which in use is placed in pressure contact both with the patient's body fluid, via capilliary tubing or a catheter, and a second diaphragm affixed to the reusable sensor. When the two diaphragms are in pressure contact, the sensor converts the pressure in the body fluid into the corresponding electrical signal and thereby provides a measurement of pressure which can be read as a visual output.
Thus, for example, U.S. Pat. No. 5,868,678 (Medex, Inc.) describes a medical pressure transducer in which a disposable fluid path component such as a dome is selectively attachable to a reusable pressure sensor component with respective fluid pressure communicating diaphragms of the components in a pressure communicating relationship. The two components are designed to be slid together by translation along a generally straight line, rather than by relative rotation, in order to reduce wear on the reusable diaphragm.
While such pressure transducers are suitable for measuring the pressure of body fluids, their accuracy or sensitivity is dependent upon both the area and degree of overlap between the two flexible membranes or diaphragms. If, for example, the membranes are not aligned axially then the pressure transmitted to the sensor may not be measured correctly. Furthermore, the linearity of signal detected may be compromised if the flexibility of one or both membranes varies across their surface and is thus more responsive to pressure in one region of the membrane (e.g. the centre).
Another problem with the pressure transducers used in the prior art is that they have a limited operating range associated with the pressure of the body fluids that they are measuring. While they are suitable for use at relatively low pressures (e.g. <5×104 Pa; 0.5 bar) they cannot be used for measuring higher pressures (e.g. in excess of 4×105 Pa, 4 bar associated with bioseparations and filtrations). Different pressure transducers are therefore necessary to measure both low and high pressures.
The component parts of the prior art transducers are generally attached to each other by snap-on connectors which can only withstand relatively low forces acting on them to pull them apart. Moreover, the capillary tubing used with these transducers tends to rupture at high pressures and flow rates. Separation, filtration, dialysis and synthesis applications used in bio-separations, for example, must typically be able to accurately measure pressures in excess of 4×105 Pa and to reliably operate at such pressures. Furthermore, the component parts of such transducers must be able to withstand forces of at least 10 N, and preferably at least 50 N, acting to separate them when they are in operable contact.
There is therefore a need within the pharmaceutical and biotechnological industries for a multi-part transducer assembly which overcomes the failings of those known in the prior art.